We present five studies aimed at developing an L1 vocabulary test for English-speaking university students. Such a test is useful as an indicator of crystallized intelligence and because vocabulary size correlates well with reading comprehension. In the first study, we tested 100 written words with four answer alternatives, based on Nation's Vocabulary Size Test. Analysis suggested two factors, which we interpreted as the possible existence of two types of difficult words: unknown words for general knowledge and unknown words for specialized knowledge. In Study 2, we attempted to develop a vocabulary test for each type of word, and these tests were then validated in Study 3. Since the test for general words proved too easy for the target population, we improved it in a fourth study by creating and testing more difficult items. Finally, a fifth study was conducted to validate the new test. Unexpectedly, Study 5 found a high correlation (r = .82) between the general knowledge vocabulary test and the specialized knowledge vocabulary test, suggesting that they measure the same latent factor, contrary to our initial assumption. Both tests have high reliability (r > .85) and correlate well (r > .4) with general knowledge, author recognition, and reading comprehension. In addition, a collection of other language tests was used and improved to verify the validity of the vocabulary tests. An exploratory factor analysis of all tests identified three factors (text comprehension, crystallized intelligence, and reading speed), with the vocabulary tests loading on the factor crystallized intelligence, which in turn correlates with reading comprehension. Structural equation modeling confirmed the interpretation.

When asked to decide if an ungrammatical sequence of words is grammatically correct or not readers find it more difficult to do so (longer response times (RTs) and more errors) if the ungrammatical sequence is created by transposing two words from a correct sentence (e.g., the white was cat big) compared with a set of matched ungrammatical sequences for which transposing any two words could not produce a correct sentence (e.g., the white was cat slowly). Here, we provide a further exploration of transposed-word effects while imposing serial reading by using rapid serial visual presentation (RSVP) in Experiments 1 (respond at the end of the sequence) and 2 (respond as soon as possible—which could be during the sequence). Crucially, in Experiment 3 we compared performance under serial RSVP conditions with parallel presentation of the same stimuli for the same total duration and with the same group of participants. We found robust transposed-word effects in the RSVP conditions tested in all experiments, but only in error rates and not in RTs. This contrasts with the effects found in both errors and RTs in our prior work using parallel presentation, as well as the parallel presentation conditions tested in Experiment 3. We provide a tentative account of why, under conditions that impose a serial word-by-word reading strategy, transposed-word effects are only seen in error rates and not in RTs.

Prior research has shown that readers may misread words by switching letters across words (e.g., the word sand in sand lane being recognized as land ). These so-called letter migration errors have been observed using a divided attention paradigm whereby two words are briefly presented simultaneously, and one is postcued for identification. Letter migrations might therefore be due to a task-induced division of attention across the two words. Here, we show that a similar rate of migration errors is obtained in a flanker paradigm in which a central target word is flanked to the left and to the right by task-irrelevant flanking words. Three words were simultaneously presented for the same brief duration. Asked to type the target word postoffset, participants produced more migration errors when the migrating letter occupied the same position in the flanker and target words, with significantly fewer migrations occurring across adjacent positions, and the effect disappearing across nonadjacent positions. Our results provide further support for the hypothesis that orthographic information spanning multiple words is processed in parallel and spatially integrated (pooled) within a single channel. It is the spatial pooling of sublexical orthographic information that is thought to drive letter migration errors.

We present five studies aimed at developing a new vocabulary test for university students. Such a test isuseful as an indication of crystallized intelligence and because vocabulary size correlates well withreading comprehension. In the first study, a list of 100 words based on Nation’s Vocabulary Size Test waspresented to 195 participants and compared to other tests of crystallized intelligence. Analysis suggestedthe presence of two distinct factors, which we interpreted as evidence for the possible existence of twotypes of difficult words: Unfamiliar words for general knowledge and unfamiliar words for specializedknowledge. In the subsequent studies we tried to develop vocabulary tests for each type of words, at thesame time trying out various reading comprehension tests to use as validation criterion. However, in thefinal study a high correlation (r =.82) was found between our two vocabulary tests, indicating that theymeasure the same latent factor, contrary to our initial assumption. Both tests have high reliability (r >.85) and correlate well (r > .4) with general knowledge, author recognition, and reading comprehension.As part of our research efforts, a collection of new and existing tests was used and (often) improved toverify the validity of the vocabulary tests. An exploratory factor analysis on all tests established 3 factors(text comprehension, crystallized intelligence, and reading rate), with the vocabulary tests loading on thefactor of crystallized intelligence, which in turn correlated with reading comprehension. Structuralequation modeling corroborated the interpretation. We end by providing an overview of the differenttests that were developed or improved throughout the studies. They are freely available for researchpurposes at https://osf.io/ef3s4/.

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